Electronic tremolo device



Aug. l1, 1959 D. J. LESLIE ELECTRONIC TREMOLO DEVICE Filed March 12, 1956 6 Sheets-Sheet l Dam/,ua JI [f5.4 /5

Aus 1l. 1959y E D. J.v LESLIE 2,899,644

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AELECTRONIC TREMOLO DEVICE Filed March 12, 1956 6 Sheets-Sheet 3 FI/6a 3a,

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6 Sheets-Sheet 4 1 INVENToR. D04/7.40 J .Lffz/f D. J. LESLIE ELECTRONIC TREMOLO DEVICE Aug. 1l, 1959 Filed March 12, 1956 Aug. ll, 1959 n. J. LESLIE l ELECTRONIC TREMOLO DEVICE Filed March 12, 1956 6 Sheets-Sheet 5 BY ffw d 72W Aug. 11, 1959 D. J. LESLIE ELECTRONIC TREMOLO DEVICE 6 Sheets-Sheet 6 Filed March 12, 1956 United States Patent 2,899,644 :ELECTRONC l1;,13121409Grim-"19E DonaldJ. Leslie, Pasadena, Calif. Application Marchi?, ;1256-Ssri,al Nef-'111,027 26 Claims. -(01.331-49) This vinvention,relates to electronic musical instruments z tridespecially to apparatus'rffor adding..trenioloorvibrato t l tricallycreat'ed tones,,suchasiyacuumitube oscillarotarymagneticor electrostatic genierators,.orfyibrat ing'reeds with associatedpick-up arrangements. i 5 Y In someinstruinents of Vvthis lcharactefr .it-. is common practiceftouse.atrernolo devicef such as a vacuum tube foscillator orfmech'anically operated voltage",varia,tion means which periodically detunes Valtone' oscillatorl fata rate of from..five toeight'cycles/perl second vinvorderfto `'obtain-the vibratoiortremoloyeiect. AIt lis wellkriown thatga l.tone `oscillator circuit maybe arranged softhat 'its frequency of .will `.be sensitive Atoonfe ofthe rect voltages' -supplied to Y'the Q illator", ,purpose ofthevibrato oscillator .orfyihfato devise isl `to supply a :varying .voltage at trerriolo-frequencies lwhicvhin turn, Qilllies' the tone` oscillator zbyQthe .desired amount'.

' `Inotlier"instrilmen'ts .rred4 frequericy gepira'tors ,are ot'ten employed, such as rotary .genrato'rsfusingmagnetic oi' electrostatic pick-up 'means orwvibratin'g reds. ,associatedpick-ups. In this class,k .of instruments a` phase shifting .network is often lemployed"that 1.ii/ill", impart ti-emol@ fand often vacuum ytunes are, used inthepliase ,shitingmetwork ,whichinay bev controlled direc-ncurrent lvoltages ,pulsating at tremololfrqueircies to cause {:,.ijyi1 1g',:amounts` of phase lsliifi to occur infthfepnetwork. ,in second classfotA instruments itis thereforefpossible to Vstop,`fstart, and l control ,tremolo .ei'fectsljy ,varying la Qiejctcurrent yoltaige'from'fa lsuitable;dei/ice. .i

` Tremol'devices past 2have beencperative to create tremolo throughout 'the duration of, the, tprre'pnov.duced by theinstrument. Howeven itisapparentthat ytefcliniques .used byartists nwith".violins ,or otherl fril- "inents',.for example, aiematerially diler i tirornl constant Ll trerrrolta.A fForeXample, "a pitchl mayb siartefdfwitliout Itrernolo and then tremolo may be gradually added inino creasedamounts and speedfuntil a.maximumis rea clied fforaparticulaitone. i' "A A i 'Iflieprinslai'yvl object ofthis invention is,to m ak e itpos- .siblefor such interpretiveeifects t'o'fbeY accornlish "d electronic muSic/al'instruments of this v lc )iynject is accompiished'by-novelcircuits 'n whichftlie tremolo oscillator or other treniolo prod c ing evizce is energiaed,or ontrolled to cause increasing amounts of tonedesired to be produced. Another object Iof this invention is to make itpossible to `incorporate such features' in an electronic musical instrumen't without'undue multiplication, of parts. A' Ariotherobject of this invention is to provide an inertia mechanism `for operating a mechanical deviceffor' producing tremolo inwhich the inertia mechanism provides an increasing speed of tremolo in accordancewith the existence of'a tone.

'I fhis Ainvention possesses many other advantages, and has other objectswhich maybe made more clearly apparent from a consideration of several embodiments of 'theinvention For lthis purpose,there are showna ,tremolo afterV operation .of Va keycorresponding to the 2,899,644 Patented Aug. 11, 1959 .,formsinthe .drawings .accompanying and forming part of the present specification. These forms will nowlbe de- Hscribed in .detaiL .illustratingythe generalprinciples of the invention; but it is .tobe `understoodthat this detailed de- Ascription.isnottohe taken -in a limiting sense, since the ,scope oftheinvention is best defined ,bythe appended .tronic .organ incorporating the present invention; vand Figs. 2,v 3,3a, 4, 5 Y'and .6 are, respectively, diagrammatic representations of an electric'organ, each incorporating modified forms of the present invention.

.In Fig'. 1, there is disclosed a series of vtone oscillators 10, ll'nand 12., the outputs of which are connected through leads 13, J14 and v15 via a common connection 1 6 to an amplifier 17 and a loud speaker 18. Only three tone generators are shown. However, it will be understood that as many tone generators areprovided as there are desired tones in the instrument.

The tone oscillators 10, 11 and 1-2 are placed in operation by manipulation of keys 19, 20 and 2 1 respectively associated with the tone oscillators. Each of thesekeys 19, 20 and 21 operates a circuit controlling arrnf22, 23 and 24 to connect thetone oscillatorto a source of current. lOn Vdepression of the key 19, for example, ythe* c ircuit controllingarm v2. 2fengages a bus 25 connected to one terminal 27 cooperable with a current source.' Another terminal 28, grounded `as at" 29, completes the connection'pair. v Y 'i i The other arms 2 3 and 24, associated with thekeys 20 and 21', rnayals'obe urged tovengage the Abusf25 which isfutilized as a common connection iorfthis'purpos'e. Depressionof any one of the keys ofthe'iristrument accordingly'places yinwoperation lthe corr'esponc ling tone oscillator`,`and musical tones arelproduced. v'

Shown by way (of examplein Fig. lare supplemental circuitcontrolling arms 3 0, 3 1 32 associatedwith the'r'espect'ive keys 19, and 2 1. Thesesupplemen-tal arms engage asecond commonjbus 33, also connectedto the ,source of Icurrent. operationof a usual organ stop providedin the instrument, the bus 3.3 rnfaybcplaced in yoperative position. Leads 34, 3 5'and 3 6, Va ssociated with the respective supplemental arms 3,0, y3,1 ar1d 32 Land cooperable with the 'hus-33, may y.establish connections to other tone oscillators corresponding tofcertain harmonics,

Any number of supplemental arms may be ,associatedvwith eachkey.

A tremolo oscillator 37 is coupled to Vallof thetone oscillators 10, 11"and 1,2','co`upling circuitsbeing indicated vby the lines 38, 39 and 4 0. The tremolo oscillatorcreates Va terminalAl through'a resistor 42 and a lead 43. A terrninal 44, grounded as at 45, cooperates with the terminal .41 to complete the coupling pair.

Normally the tremolo oscillator .37 is ineffective to create a signal. This is accomplished by normally grounding the plate connection or lead 43. For this purpose, a normally closed relay Ioperated switch 46 is provided. rThe movable arm 47 of ,th,e switch 46 is grounded as at `48. The .contac'tl 49, normally engaged by the a rm 47, conncctswith the plate lead .43 through a small resistor 50, a connectionpoint '51 being indicatedat the plate lead The function` of the resistorfwill `be described hereinafter. The resistanceof the resistor 42 is'rnany times as great as that of the resistor Si). As aspecificex- 3 ohms, and the resistor 50 may have a resistance of about ten ohms. The connection point 51 and the anode of oscillator 37 are, accordingly, substantially at the poteni tial of the ground connection 48 when the switch 46 is closed. u

When the switch 46 is opened, plate supply voltage 1s available to the tremolo oscillator 37 since the ground to one side of a battery '7. The other side of the battery 57 is connected to one terminal of the relay coil 52. The other treminal of the relay coil 52 connects with a common connection 5S. Each of the circuit controlling arms 53, 54 and 55 is connected to the common connection 58 and is engageable with the bus 56. Should the key 19 be depressed, for example, corresponding to energization of the tone oscillator 10, an energization circuit for the relay coil 52 will be completed as follows: One side of the battery 57, common bus 56, circuit controlling arm 53, common connection 58, through the relay 52, through the other side of the battery 57. All of the circuit controlling arms 53, 54 and 55 engageable with the common bus 56 are in parallel relationship.

When the ground connection established by the switch 46 is interrupted, plate supply voltage is increased slowly. For this purpose, a capacitor 59 is provided that connects between a ground connection 60 and the connection point 51. The capacitor 59 opposes instantaneous build-up of voltage to the tremolo oscillator.

As the plate supply voltage to the tremolo oscillator 37 slowly builds up, the amplitude and speed of tremolo are correspondingly increased. The amplitude transient characteristics are achieved by making the capacity of the capacitor 59 approximately ten microfarads. The increasing speed of the tremolo is accomplished by the change of tuning of the tremolo oscillator due to the increasing vacuum tube plate current which gradually decreases the tuning inductance as the plate current increases through saturation effects. They key must be depressed for a certain length of time before maximum tremolo effeet and speed are achieved. Appropriate interpretive effects are accordingly provided that correspond to interpretive effects often employed by artists.

The small resistor 50 prevents arcing when the switch 46 is again closed.

In the form shown in Fig. 2, the lead 61 to the tremolo oscillator 62 is normally grounded in a slightly diiferent manner. A lead 63, connecting through the lO-ohm resistor to the connection point 64 and the tremolo plate lead 61, is connected to a ground connection 65 through serially inserted, normally closed switches 66, 67, etc. associated with respective keys 68, 69, etc. On depression of any of the keys, the ground connection at 65 is interrupted and plate supply voltage may be applied to the tremolo oscillator 62. 'Ihe apparatus shown in Fig. 2 Ictherlvise operates in a manner similar to that shown in In the form shown in Fig. 3, the plate lead 70 to the tremolo oscillator 71, coupled to the various tone generators 72, is normally grounded by a relay operated switch 73. The arm 74 of the switch 73 is resiliently biased so that it normally does not engage the contact 75 of the switch. A relay coil 76 is energized to close the switch except when a circuit is established to any of the tone generators 72. Accordingly, on operation of the key 77, for example, the relay coil 76 is deenergized and the ground connection 78 to the switch arm 74 and contact 75 is interrupted so that the tremolo oscillator 71 is supplied with plate voltage.

A circuit structure utilizing a vacuum tube 79 is re- 4 sponsive to the existence of current to any of the tone oscillators 72. ri`he vacuum tube 79, which includes a cathode 80, a grid 31 and a plate S2, conducts current only when current is not supplied to any of the generators 72. The coil 76 is in the plate circuit of the vacuum tube 79. An explanation of the operation of this vacuum tube operated relay is as follows:

A lead 83 connects the cathode 80 to a plus 75-volt tap 84 through a biasing battery 85 which furnishes the proper amount of grid bias voltage to cut off all plate current in tube 79 if there are no other external potentials applied between grid and cathode. A lead 86 into which the coil 76 is serially inserted connects the plate S2 to a 30G-volt tap 87. A lead S8 from the grid 81 connects through serially joined resistors 89 and 90 to the 300- volt tap 87. The resistors 89 and 90 have resistance of about two megohms and oneV megohm respectively.

The oscillators 72 are energized from the 75-volt tap 84. A one-way conductor or rectifier 91 is inserted between a common bus 92 engaged by corresponding arms 93 associated with the various keys 77 and the tap 84 for purposes to be presently described.

A sensing connection 94 extends from between the resistors 89 and 9) in the grid circuit to a point 95 between the rectifier and bus bar 92 of the energization circuits for the tone oscillators. When the key 77 is in its ol position, the sensing connection at 95 rises above 75 volts due to the connection of resistor 9) to the 30D-Volt tap. The value of voltage at 95 will be limited to below 300 volts due to the back resistance of the rectier 91, as the resistor and the back resistance of the rectifier 91 form a voltage divider between the 30G-volt tap and the 7 5-volt tap. Itis well known that the back resistance of a properly selected rectifier will be high compared to its forward resistance and, therefore, the voltage rise at point will be definite and reliable when the arm 93 does not make contact with the bus 92.

With the connection 94 at a value higher than 75 volts, for instance volts, the potential of the grid 81 is raised in a positive direction due to the connection of resistor 89 to the point 95. Since the grid will start to permit passage of current to the cathode when it reaches the same potential as the cathode, the value of the voltage at connection 88 will rise no higher than the cathode potential; also, because the resistor 89 has a high resistance value, the grid current will be limited to a low value. The net result of the tube operation is that the actual positive value at point 95 may vary over wide limits, but voltages above those necessary to bring the grid to the same potential as the cathode will appear as a voltage drop across the resistor 89 and, therefore, the operation of the tube 79 will not be critical to the voltage supplied at connection 94 as long as there is a minimum value available to bring the grid up to the cathode potential.

With the key 77 in its off position, therefore, the grid will conduct slightly and eliminate grid-cathode bias, causing plate current to flow through coil 76 which, in turn, will operate arm 74 to close contact 75 and ground the plate supply to the tremolo oscillator through ground 78 and the 10-ohm resistor.

When key 77 is operated, the rectifier 91 conducts through a very low forward resistance between the 75-volt tap and the point 95 because even one tone oscillator requires more current than can be supplied through resistor 90. This set of conditions then provides sensing conductor 94 with 75 volts and, under these conditions, the biasing battery will supply sufficient grid bias to prevent conduction of plate 82. Accordingly, the relay ,73 is deenergized and the switch arm 74 moves away from the contact 75, ungrounding the plate supply lead 70 tothe tremolo oscillator.V

In all other respects the arrangement shown in Fig. 3

is similar to that shown in Fig.l 1 or 2, the capacitor 96 controlling the build-up of vpl'tage to the tremoloosculata; 7.1.-`I`

.Annilein operabieswnch 9.1 .parallels .the rectifier .so

.thatthe .sensing7 voltage. point .at 94 remains .at 75 V.toits- Lilnder these .oo tions, LthooiosibattervS prevents plate current Ain tube ,9, thereby. allowing contact 75 to. remain open so that ,tremolo lis applied continuously whether key 77 is operated or not. T he switch 97 accordingly achieves `alternate modes of operation of the instrument.

.In .the .form .Shown iuFis. 3 ,the .apparatus Senses the existence of operation vof the tone oscillators '7,2 without d rainingpower frjom the circuits for the tone oscillators. This is especially important where .the tuning of the oscillators depends .upon a well regulated voltage source. QIf the oswcillatorsare of such character as to permit power `drains from the circuits without-.altering the tuning of the 0.SQillat 0 r s, n sirnplerarrangernent can beprovided. Thus, in Fig. 3a a relay coil220 is. serially inserted between a CQmmon bus 2,21 and one of the terminals 222 of a .vibratooscillators 227. Vibrato or tremolo is accordingly .permitted to ,build up.

The systems heretofore described may be subject toa certain disadvantage. Ifonekey is vdepressedand a sec- .pnd keyisfoperatedbefore therelease of theiirst key, the tremolo oscillatoris already in operationwhen the second key 1s depressed. The full tremolo eiecton the second tone .will .then be immediate and coincidental with the tone itself. In order that the tremolo effects start to buildup `with the depression of each key, asmanytremolo oscillators and control circuits could be provided as there .arekeys However, such an arrangement would .unduly multiply the equipment necessary.

In Fig. 4 there is'diagramrnatically illustrated a system wherein -sixtremolo oscillators .101, 102, 103, 104, 105

and 106 can beconnectedin a manner so as to approximate this result. Grounding devices or energization building controls 111, 112, 113, 114, 115 and 116 and six electrical channels 121, 122, 123, 124, 125 and 126 areassociated, respectively with the tremolooscillators. Leads from a keyboard 100 indicate that upon .depression of the corresponding. keys, certain connections are made to influence one of the tremolo oscillators. The

.lead 107 associated with C1, for example, establishes an energ1zation circuit in channel 122 to the tremolo oscillator 102.

Other keys` cause energization of the tremolo oscillator .and Dei, allas indicated by the leads between thechannel 1 22 and the keyboard 100.

The segregation amongthe channels is as follows:

.A .segregationsuch .as this is made in view of the probability of notes being consecutively sounded. For example, there is only a small probability that C1 and D2 will be simultaneously sounded or sounded in rapid succession. Accordingly, by virtue of this segregation, itis vexpected that during the course of playing the instrument, the respectiveitremolo oscillators will be for the` most v part controlled by thelength oftime that a particular f,.key, is operative. .As an. example, if Dl and Fli are sounded in f.sequenceand F1# is .operative prior to the time that@ iS .ioonetotve y.the following-.operation .Will

.result .Thetfemolo oselieto,llwilllbe-onerstive upon .initial depression of .the key oorreoroosog toDi. andthe tremolo will inofeese in .ooeerdooee with .thetime that .the vkey'Dl is operative. `The tremolo oscillator 103, operative to impose ltremolonon F15, is not operativqDl being ineffective to operate zthat oscillator. WhenFlit'isHoperated, energization for tremolo oscillations will n be iinereosed from the time. that Fit is. ,Operetei The venergizatiqn controls may takethe form shown in Fig. 1,2 or 3.

1.o .the form .shown .in .Fig- :3. the..e.er.isin.s.e9t1neetion existing electronic organ, designato :senswentheexistence of atoneat theoutput oftheV oscillators.

Fis- 5 diasrammatieally i111@ rates .o .SYStem .Qfthis character. The `pedalswitches ,13 0, lower and upper .manual .switehes 131 .and llore-illustroted.byhloek diagrams. Pedal oscillators 13,3, operatedl by the pedal switches 130, are similarly illustrated. The.blocksc1`3 `4 and 135 lindicate Ygroupsffof oscillators respectively lfor the lower and upper manuals.

The. lower .and .upperfmamtaioscillators .ltondls are.'indicateduashaving `two types of .outputrfor each tone. V,The lines I3-6wand 1 38 designate groups vof tinteltype output connectionsl from the respective lower land .uppervmanual o svcillators 1 3 4 and 135. Lines137 and `139inclicate groups of string-type output connections .from the .respective manual oscillators 134 and`13x5. A v.line .140 indicates output` connections from the .pedal osoillators v1.3.1"- .Impulses .are then transmitted .toffon amplifier141 and aspeaker system 1,42 by'tlieidvofa .rnixer circuit indicated byfthe ,block` 1 43. Appropriate .stop tablet controls may voperate appropriatedevicesnfor `Selecting .the .impulses transmitted throltgh the circuity 1,43. v

,Vibrato ,oscillators 144 ivand 1 45 are :associated Ayvith `someof the oscillators in,groups, 13 4 and 155, as, lfor example. vthose osoillotors Vproeiueing .string-.type .outputs- The lbuild-up Aof `vibrato oscillations produced 4by .the vibrato oscillators .135 iscontrolled in almannersiinilar 4 to.that,of Eligsrl, 2 and 3.

VPlate-.voltage impressed .across terminalsd148and 1,49

`is `conducted to .the .vibrato oscillator 145 serially through ahighlresistance 11.47 connect-edt() theterniinal 14,8,.,and,afconnection146. The other terminal 149` is grounded. The arm of arelay-lnormallyjengages a grounded contact andA grounds the plate connection i146,

.aresistor'of smallresistance 151 being serial1y associated ,with the arm of the relay and (the plate ccnnection146. .Uponopening of the.relay150,the plate .connection.146isyungrounded and the voltageis permitted to buildfupns inthefprevious forms.

j'The relay. 150. `is controlledbya relay coil.153 inthe output-.oirouit of an .electronic Sensingdeviee V .instit/Meh may incorporate-ayacnum tube asin the form. shown in Fig. 3. The eleotronio Sensinaoevioe. .154.oouses ener- .gization or deenergization of thejcoil 1 53inu accordance with the existence or non-existence of an impulse at the output sconnections l139 corresponding. to the ystring-type oscillations. Thisis diagrammatically:illustratedby the connection 155.

An .amplier.:156, serially inserted atfthe connection 15,5, provides. lappropriate signal. strength for control of the device 154.

Upon the existence of string-type tones from the .upper manualoscillatorsilSS, the.r.elay-153` is energized tov un- .ground the plate connection .1.46.

Ifdesired, a plnralityof ,vibrato ,oscillators .in place of the singleoscillatorsa145 Inaytbeprovided associated v.with corresponding'numbers .of sensing-.devices 154 segre- .soted in a manoeotdesoribed in connection .with'Fia1 4.

.Infla 6;the.re'.is diagrammatioaiiy illustrated-,ternur- .oosessof example, aofeleotIonioorganutilizing vibrating L reeds 160, 161, etc. for the purpose of producing impulses corresponding to the tones throughout the musical range of the instrument. The reeds, in a well known manner, are vibrated by a current of air. The length of the reeds 160, 161, etc. is carefully controlled to determine the appropriate fundamental frequencies. The reeds 160 and 161 are opposed to tone screw pick-ups 162 and 163 to which direct current voltage is selectively applied when it is desired that the reeds 160 and 161 be operative. Each reed 160 or 161 in cooperation with its respective pick-up 162 or 163 forms a capacitor, the capacity of which cyclically changes in accordance with the vibration of the reeds. This induces a flow of alternating current in connections 164 and 165 connected to the respective reeds 160 and 161.

A common connection 166 is coupled to an amplier 167 and a speaker system 168 in a manner to be hereinafter described. Circuit controllers 169, 170, etc., respectively associated with keys, Voperate to polarize the respective tone screw pick-ups 162, 163, etc. For this purpose, the circuit controller arms 169, 170 cooperate with a common bus 173 to which a direct current potential is applied.

The common connection 166 cooperates with a phase shift network 174 that has various taps numbered 0, l, 2, 3, 4, 5, 6, 7 and 8 representing, respectively, successively increasing amounts of phase shift with respect to the impulses as it appears at the common connection 166. The connection 175 to the amplifier is cyclically associated with the taps to 8 in continuous sequence by the aid of a rotary scanner 176. The cyclically varying phase shift operates to impose vibrato effect in a well known manner. The taps of the phase shift network 174 respectively connect with condenser plates located circularly about the scanner 176. A revolvable arm 177, connected as by a brush to the amplifier connection 175, carries a condenser plate 178 that is moved into coupling relationship with the circularly arranged condenser plates to establish a coupling. Upon rotation of the arm 177,

the amplifier connection 175 is effectively coupled in sequence to the taps 0, l, 2, 3, 4, 5, 6, 7, 8, 7, 6, 5, 4, 3, 2, l, 0, etc. The cyclical variation is achieved by providing two symmetrically arranged condenser plates connected to each of the taps l, 2, 3, 4, 5, 6, and 7. The arm 177 is mounted upon a shaft 179 and carries at one end a cylindrical shell 180. A bearing 181 supports the shaft near the shell 180. A magnetic device 182, supported upon a shaft 183 aligned with but separate from the shaft 179, is continuously rotated. The magnetic device 182 its with slight clearance into the shell 180 and tends to rotate the shell 180. The shaft 183 is supported by a bearing 184. A pulley wheel 185 is engaged by a belt 186 which, in turn, cooperates with a pulley 187 mounted upon a shaft of a motor 188.

The shaft 179, upon which the scanner arm 177 is mounted, is normally restrained from the rotation by the aid of a brake structure 189. The brake includes a wheel 190, mounted upon the shaft 179, and a friction band 191, one end of which is mounted upon a stationary bracket y192. The other end of the band 191 is normally urged into wrapping relationship with the wheel 190 by the aid of a spring 193, accordingly preventing rotation of the shaft 179 and the arm 177. Under this condition, there is no change in phase relationship between the amplier connection 175 and the common connection 166, the arm 177 being stationary, and no vibrato is added.

The band 191 is released by a solenoid 194 that is energized upon depression of any of the keys 171, 172, etc. For this purpose, supplemental circuit controlling arms 195, 19,6, etc. are respectively associated with the keys 171 and 172. Each of the circuit controlling arms 195 connects with a common connection 197 that is connected to one side of a battery 198. The arms 195, 196, '.etc. are'engageable with a common bus 199 that connects through the solenoid coil 200 to the opposite side of the battery 198. Thus, upon depression of any of the keys, an energization circuit is completed for the solenoid 194, and the brake band 191 is removed to releasing position. The shell is thus free to rotate and the shaft 179 comes up to speed.

Conveniently, the wheel forms an inertia element so that the rate that the speed of the shaft 179 increases is limited. Accordingly, upon release of the band 191, as by operation of any of the keys, the speed of rotation of the scanner arm 177 increases slowly and the rate of change of phase shift correspondingly increases. Vibrato oscillations accordingly build up in speed in accordance with the time interval of operation of the keys 171, 172, etc. When the key is released, an energization circuit for the solenoid 194 is interrupted and causes the band 193 to engage the wheel 190 quickly to cause a cessation in the rotation of the shaft 179.

It is obvious that many modifications, so far as adaptations of the systems described herein are concerned, may be made without departing from the broader aspects of this invention.

Vibrato and tremolo are recognized as producing similar effects. In fact, the terms are often used interchangeably by musicians. So far as the present invention is concerned, it will readily be appreciated that the controls and circuits may be used either for tremolo or vibrato systems or for combined systems. Since no term generic to tremolo and vibrato is known, the term Vibrato, so far as used in the appended claims, will be understood as meaning trernolo or vibrato or both.

The inventor claims:

1. In an electrical musical instrument utilizing a tone osciilator and a playing key depressible for causing the tone oscillator to be effective: a vibrato oscillator having an anode and a source of potential connected to the anode; a circuit coupling the oscillators for aecting the output tone of the tone oscillator by aid of the vibrato oscillator; and circuit means operable upon depression of the playing key for modifying the potential of the anode for causing the vibrato oscillator to become increasingly active.

2. In a musical instrument: an electrical tone generator; selective means for controlling the output of impulses by the tone generator; a vibrato device increasingly operative only upon operation of the controlling means; and means for limiting the rate at which the output of the device increases after initial operation thereof.

3. In a'musical instrument: means for producing an electrical impulse corresponding to a tone; means for controlling the output of impulses by the tone producing means; means for increasingly adding vibrato to the impulse and operative only upon output of impulses by the tone producing means; and means for limiting the buildup of the vibrato produced by said vibrato adding means.

4. In a musical instrument: means for producing an electrical impulse corresponding to a musical tone; selective means controlling the output of impulses by the impulse producing means; electrically energizable means for producing vibrato in amounts dependent upon the eX- tent olf energization thereof; an energization circuit for the vibrato producing means; means cooperable with the energization circuit for normally determining a minimum energization of said vibrato producing means; means operative upon the existence of output from the impulse producing means for interrupting operation of said minimum energization determining means; and tirne delay means for limiting the rate of increasing energization of the vibrato producing means after operation of said minimum energization determining fmeans is interrupted.

5. In a musical instrument: a vibrato oscillator; an energization circuit for the vibrato oscillator; a relay operated switch normally preventing energizationvof the vibrato oscillator and operable to permit energization of saidA vibrato oscillator; a series of tone oscillators; controllers selectively .operative `to cause thetone oscillators .tobeleiiective;` a coupling between the vibrato oscillator .and `at .least .some of the tone oscillators; circuit means .effective upon operation of. any one of at least-some of `the controllers foroperating the relay operated switch; .and .time delay .means controlling the rate ofincrease `of energizationof the vibrato oscillator,

f6. In-a musical instrument: a vibratoy producing device; .means ,providing an energization vcircuit'for the vibrato fdevice; aseries of meansfor ,producingelectrical impulses corresponding tol-musical tones; controllers Afor the im- 'pulseproducing means; means 'for causing the vibrato 'device-to `add vibrato to the impulses; aseries of switches associated with-the controllers and closed only when the controllers are in inoperative, position; connection means connecting the switches in .series and determining'acir- .'cuit relationship only when all of the switches are closed `to prevent energization of .the vibrato device; Yand time delay means controlling the rate of increase-ofsenergization of lthe vibrato device.

v7.5In a musical instrument: means for producingelectrical impulses corresponding to musical. tones; `a vibrato producing ldevice; an--energization circuit 'for the-vibrato device; a relay operated rswitch normally s preventing venergization of`the vibrato device andgoperableI 'to .permit energization of the vibrato device; means'for causing [the 'vibrato device to addvibrato to the impulses; acontrol device Ahaving an input circuit and output circuit, the output circuit including relay -means 4for operating said switch, "the input circuit including means dependentupon "th'eoutput of impulsesv by any one of the impulse producing means; and time delay means controllingvthe'rate `of 'increase .of energization oftthe vibrato device.

8."In a musical instrument: tone oscillators; a vibrato oscillator; an energization-.circuit'for the vibrato oscilla- "the .rate of increase .of energization of v.the vibratozoscilz;

"lat'or y:9. In 'a'musicalinstrumentz meansfor producing elec- "tricahim'pulses corresponding to musical,tones;.fanzenere "gizatlonco'ntrol circuit for Isaid meansincluding .a runidirectional conductor and circuit controllers; ,a vibrato' idevice; means for .causing the `vibrato .device .to .add vibr'ato to `the impulses; an electronicdevicevhaving an input 'circuit and an output circuit, .theoutput circuit includingmeans for. permitting and ,preventingenergization ofsaid vibrato device in accordance ywithlthe conditionof..

'operation'of said 4electronic device; .meanszbiasing .the input circuitfor one mode of operation.` of the electronic "device'in which energization of said vibratofdevice is ,jpreventeda sensing connection between. theinputtcircuit `and `one side of said conductor; the vcircuitcontrollers, 'when operative, causing a row ofcurrent through .the conductor toimpose a different biasing :voltage onmsaid input circuit to cause another mode of operation .of said device in which energization of said vibrato device is permitted; and time delay means controlling=thexrate of increase ot energization of the vibrato device.

10. In an electrical musical instrument: a series of Etone oscillators;,a.series of.circuit controllers for'the tone oscillators; electrically .common means cooperable I' with f? the circuiti controllershandA connectedthrough a-funidirec-- electrodes and a control electrode; .an output circuit `between the pair of electrodes, ,and `including meansfor moving the switch;a circuit for the control electrodeconnected to a` second source of direct current lat a potential higher than that of said iirst source Ato determine a mode of operationof said output circuit in which said switch is in said one position; asensing connection connected ,to Ythe Vcontrol electrode and `to the common means, and `operable upon conduction through said Yconductor to connect said `rst source to said control electrodeto determine a mode -of operation of said ,output circuit in `which said switch is in another position; and timedelay means for limitingrthe rate of increase of energizationof said vibrato oscillator.

1l. In an velectrical ,musical instrument: `a series of tone oscillators; a ,series of circuit controllersfor thertone oscillators; electrically common ,means cooperable `with Vthe vcircuit.,controllers .and connected Athrough a unidirectional conductor with `a lfirstsource of ,direct current; .a vibrato oscillator coupled to atleast some of the ttone oscillators; a switch; an energization circuit for -the vibratoroscillatorand dependent upon the switch being in onefposition; an electronic device vhaving a pair of Y.electrodesand a control electrode; an output circuit be- .tweenthe pair of electrodes, and including meansfor moving ,thevswitch; a circuitfor thecontroly electrode `connectedlto a ,secondsource `of Ydirect current at a potential higher than that of `said firstsourcesto determine a mode .of operation of Vsaid ,output circuit in which said switch is.in said VAone position; a sensing connection connected tothelcontrol electrode andfto 'the commonmeans, and loperableupon-fconduction through said conductor to connect said "rst source to said control velectrode to determiuea mode of operation of said output circuit in which saidswitch'iisinanother position; 'time `delay means for limiting the rate of increaseo'f energization of said vibratooscillator;Aandgmeans for selectively shunting `said unidirectional conductor in order continuously to connect ksaid,first source to said control electrode.

l2. fIn ,a musical instrument: as plurality of means for producing electrical impulses corresponding to musical tones; selective means controlling the output of impulses ,by `Sad ,impulse .producing means; a series of vibrato devices; means for causing the vibrato devices to impose vibratoon the impulses created by separate groups of impulse. producing means respectively; means responsive `to output of impulses from any of said impulse producing means for energizing the corresponding vibrato device; and time delay means for detenmininga slow rate of in- --creasing energization of `the vibrato device.

113.",In amusical instrument: aplurality of means for producing "electrical impulses corresponding to vmusical tones; selective means controlling theoutput of-impulses by said-impulse producing means; a series of vibrato *devices;means"for causing the vibrato devices to impose vibratoon the 4impulses produced respectively by groups lof nnpulselproducing mea-ns;.means initiated upon the existence of output of impulses` from said impulse producing means for energizingA that vibrato device associated v'ivith'the groupin which saidV impulse producing means is included; and vtime' delay means for limiting the rate at which'theenergization of each vibrato device increases.

A`1'4."In a musical instrument: a plurality of tone oscil- `4lators; a set of vibrato oscillators, each coupled to a sgroup ofrtone oscillators; means initiated upon effective operation nof-a tone oscillator for energizing that vibrato voscillatoncoupled tothe group in which said tone osciltlator is included; and time delay means for determining Vaslow irate of increasing` energization of each vibrato oscillator, the tone generators being. so grouped that suc- 'fces'siveeoperationof tones in `any one group is unlikely in a musical composition.

15. In a musical instrument: a series of electrical tone generators creating impulses corresponding to musical notes in a plurality of octaves; playing keys controlling the output of impulses by the generators; a set of six vibrato devices, each operable to impose vibrato on impulses of a group of tone generators, each group including generators for two tones in each octave; means initiated upon effective operation of a tone generator in any one group for causing operation of the corresponding vibrato device; and time delay means for limiting the rate at which the output of each vibrato device increases.

16. In a musical instrument: a series of electrical tone generators creating impulses corresponding to musical notes in a plurality of octaves; playing keys controlling the output of impulses by the generators; a set of six vibrato devices, each operable to impose vibrato on impulses of a group of tone generators, each group including generators for two consecutive half tones in alternate octaves and next consecutive two half tones in the other octaves; means initiated upon operation of a tone generator in any one group -for causing operation of the corresponding vibrato device; and time delay means for limiting the rate at which the output of each vibrato device increases. l y

17. In a musical instrument: a vibrato oscillator having a plate circuit including an inductance element, the reactance of which decreases upon an increase in plate current; means supplying plate energization for the vibrato oscillator; means for producing an electrical impulse corresponding to a musical tone; means for causing the vibrato oscillator to superimpose vibrato oscillations on the electrical impulse; means cooperable with the plate current supplying means for normally determining minimum plate current for the vibrato oscillator;

kmeans responsive to the operation of said impulse producing means for interrupting operation of said minimum plate current determining means to permit build-up of plate energizat-ion; and time delay means for limiting the rate of increasing plate energization of the vibrato oscillator after interruption of said minimum plate eurrent determining means.

18. In a musical instrument: means for producing electrical impulses corresponding to musical tones; a vibrato producing device; an energization circuit for the vibrato device; means including a relay operated switch normally preventing energization of the vibrato device; means for causing the vibrato device to add vibrato to the impulses; means sensing the existence of an impulse for determining the position of said switch; and time delay means controlling the rate of increase of energization of the vibrato device.

19. In a musical instrument: means for producing electrical impulses corresponding to musical tones; selective means for controlling the output of impulses from said impulse producing means; rotary means operable to produce vibrato in amounts corresponding to the speed of'said rotary means; means normally preventing rotation of said rotary means; means for initiating rotation of said rotary means upon the existence of an output impulse; and means limiting the rate of increase of rotation of said rotary means.

20. In a musical instrument: means for producing electrical impulses corresponding to musical tones; selective means for controlling the output of impulses from said impulse producing means; a rotary device operable to produce vibrato in amounts corresponding to thev speed of said rotary means; a brake normally preventing rotation of the rotary device; a slipping clutch for connecting tlierotary device to a drive; and means for releasing the brake only upon the existence of an' output impulse; the inertia of the rotary device determining a slow rate of increase of rotation of said rotary device.

2l. In a musical instrument: means for producing 12 electrical impulses corresponding to musical tones; selective means for controlling the output of impulses from said impulse producing means; a rotary device operable to produce vibrato in amounts corresopnding to the speed of said rotary means; a irst magnetic clutch element carried by the rotary device; a second magnetic clutch element adapted to be continuously rotated and in operative relationship with the first magnetic clutch element; an inertia member carried by the rotary device; a band cooperable with the inertia member for holding the rotary device `against rotation; resilient means urging the band into engagement with the inertia member; electromagnetic means for releasing the band; and means operative upon the existence of an output impulse for energizing the electromagnetic means.

22. In a musical instrument: means for producing a tone corresponding to va musical note; a key movable to one position for operating said means; and means for producing vibrato in increasing amounts dependent upon the period that the key is in said one position.

23. In a musical instrument: means for producing electrical impulses corresponding to musical tones; an operating circuit for said impulse produc-.ing means; `selectively operable key means for controlling the output of impulses; a relay coil in circuit relationship with said operating circuit; electrically operated means for producing vibrato; means for initiating operation of said vibrato producing means only upon energization of said relay coil; and means limiting the rate of increase of vibrato after operation of said vibrato producing means is initiated.

24. In an electrical musical instrument: a series of tone oscillators; selectively operated control circuits for the tone oscillators for determining the tones produced by the instrument; means for adding vibrato; means responsive to tone producing operation of a control circuit for initating operation of the vibrato means; and means determining a limited rate of increase of vibrato produced'by said vibrato means after initiation of the operation of said vibrato means.

25. In an electrical musical instrument: Va series of tone oscillators; selectively operated control circuits for the oscillators for determining the tones produced by the instrument; means for adding vibrato; means controlling the operation of the vibrato means, including a circuit controller movable in response to tone producing operation of a control circuit, for limiting the rate at which the output of the vibrato means increases upon operation of said one control circuit.

26. In an electrical musical instrument: a series of tone oscillators; energization circuits for ythe tone oscillators; selectively operated control circuits for the oscillatorsrfor determining the tones produced by the instrument; common means for adding vibrato; an operating circuit for initiation of the operation of the vibrato means, including a circuit controller that must be in one position for operation of the vibrato means; a common electromagnetic coil in circuit relationship with said control circuits for moving said circuit controller to said one position only in response to tone producing operatlon of any one of the control circuits; and means determining a limited rate of increasing output by said vibrato means.

' Chick Oct. 30, 1956 

